1. Field of the Invention
The invention relates to a cushion-shaped concentrator for concentrating electromagnetic radiation, in particular solar radiation, in an absorber, comprising a transparent membrane that faces the incoming radiation during operation and a reflector membrane that reflects the incident radiation in the direction of the absorber.
2. The Prior Art
AT 505 075 B1 discloses an inflatable solar collector composed of at least two chambers that are separated by a unilaterally reflective reflector membrane and that are adapted to be impacted with a gas independently of each other. An elongate absorber is arranged above the reflector membrane in the region of the skin surface of the tubular casing. The curvature of the reflector membrane required for reflecting the incident solar radiation in the absorber is achieved in that the two chambers are each charged with different pressures. This solar collector basically operates perfectly and is, for instance, suited for smaller terrestrial solar plants.
US 2004/027310 A1 describes a ball-shaped casing for concentrating solar radiation. The ball-shaped casing is divided by a mirror into two substantially hemispherical chambers between which a pressure difference is maintained.
Accordingly, this prior art requires at least an outer casing and a reflector membrane or a mirror, respectively, arranged in the interior of the casing, which necessitates complex manufacturing. Moreover, this arrangement causes a poor land use since the concentrators have to be positioned with a considerable distance to each other so as to minimize the mutual shadowing in the morning and in the evening.
DE 10 2008 020 851 A1 discloses, on the one hand, an inflatable cushion assuming a paraboloidal shape in the inflated condition. The incoming radiation is coupled, by a reflector membrane via a coupling mirror, into a light-conducting stay tube guiding the radiation energy via a light conductor to an absorber. Accordingly, the absorber is here arranged outside of the cushion. Additionally, a film-parabolic-trough-module is described which is formed as a “rondel” and has a cover construction. This cover construction comprises a cover at which a parabolic trough arrangement with a mirror film is suspended which concentrates the incoming solar radiation on absorber tubes. Moreover, an arrangement of rods is provided which serves to stabilize the transparent cover. The suspension of the film, however, depends on gravity, so that a change of position would have an effect on the shape of the film. Accordingly, this design is not suited for a flexibly relocatable arrangement.
EP 0 050 697 A1 discloses a concentrator in the shape of an aerodynamic wing comprising a transparent film and a support structure enclosed by a skin. The upper side of the support structure is covered with a reflective film forming along with the transparent film a cushion that is filled with gas at overpressure, so that the film is convexly curved. The incoming radiation is concentrated in an absorber system that is arranged outside of the cushion. In addition, a network is provided that transfers part of the forces to the support structure, so that it is possible to make the film thin. The quasi homogeneous support structure that may be manufactured of rigid foam or a similar material may be replaced by a support framework of struts and ribs. Thus, a complex support structure or an appropriate support framework arranged outside of the cushion is required to achieve the desired shape of the concentrator.
U.S. Pat. No. 5,990,851 discloses a different antenna structure conceived to be used in space, comprising a reflector surface that is supported by a carrying structure in the form of a tube having the shape of a circular ring. The antenna structure further comprises a tension structure formed by a collapsible network of vertical connecting elements extending diagonally or in circumferential direction (belts, bands, etc.). The reflector film is fastened to vertical connecting elements such that a focusing (parabolic) surface is formed.
GB 1 602 434 discloses a solar collector with a reflector and a transparent cover portion. For stabilization of the arrangement, a framework structure applied outside is provided which carries an arm with an absorber fastened thereto.
DE 20 2007 000 702 U1 describes a tracking system for a photovoltaic power plant mounted on a floating island.
DE 100 58 065 A1 discloses an inflatable reflector, for instance, for a parabolic antenna, comprising a plurality of inflatable chambers that are arranged at a joint support wall coated with an electromagnetically and/or optically reflective layer. The support wall may be fastened with a fastening network of ropes or the like.